The disclosure relates generally to side-facet couplers having external mounting surfaces molded as an internal recess surface to facilitate alignment of optical connections to optical side-facets of a waveguide.
Optical waveguide devices formed on planar substrates have become important elements for various optical network applications. These optical network applications include multiplexers and demultiplexers in dense wavelength division multiplexing (DWDM) systems, as well as components in passive optical networks (PON).
In this regard, FIG. 1 is a cross-sectional view of an optical waveguide board assembly 10 formed on a planar substrate 12. On the planar substrate 12, there are a lower cladding layer 14, a core layer 16, and an upper cladding layer 18. These layers may be made of pure silicon or silicon dioxide (SiO2). Light travels through the core layer 16. Optical signals are received from and provided by the waveguide board assembly 10 via facets 20 of the core layer 16. In this example, facets 20 are side-facets formed in a side surface 22 of the waveguide board assembly 10, thereby providing optical connectivity for the waveguide board assembly 10 via the side surface 22. However, optically connecting a fiber optic connector to the side-facets 20 may be difficult, because a distance between an external connection surface and internal connection features of a coupler (e.g., alignment bores) must be repeatably manufactured within prescribed tolerances. If the tolerances for these distances vary beyond these prescribed tolerances, the distances between the alignment features of a coupler edge-mounted to the waveguide board assembly 10 and the side-facets 20 of the waveguides may be inaccurate, causing a coupled fiber optic connector to be misaligned with the side-facets 20 of the waveguide board assembly 10. Connection misalignment may cause attenuation and/or signal loss of the fiber optic connections.
Many factors contribute to the difficulty in aligning external components with side-facet waveguides such as waveguide board assembly 10 in FIG. 1. For example, many commonly used silicon waveguides have a physical cross section of 200 nm×200 nm or smaller. The mode field diameter, i.e., distribution of irradiance across the face of the core layer 16, may also be three microns (3μ) or less. The numerical aperture (NA) of the waveguide, i.e., the range of angles over which the system can accept or emit light, may also be very different from the NA of the optical fibers being coupled to the waveguide. These and other properties all contribute to the need for highly accurate alignment mechanisms having high mechanical stability over a wide range of temperatures.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.